Numerous pacing modalities exist which automatically adjust a cardiac pacing rate in response to sensor feedback. Typically a lower pacing rate is set at a minimum rate to maintain a base heart rate. Sensors that indicate a change metabolic need, such as activity sensors and minute ventilation sensors, are used in rate responsive pacemakers to adjust the pacing rate in response to a change in metabolic demand in closed-loop pacing rate control algorithms. A maximum upper rate is typically set as a nominal pacing rate that limits the sensor-indicated pacing rate.
Other examples of pacing modalities that can increase a pacing rate above a programmed lower rate include various tachycardia prevention pacing modalities, such as rate stabilization or rate smoothing pacing, atrial and ventricular overdrive pacing, post-mode switch overdrive pacing, and atrial preferred pacing. These various automatic rate-adjusting pacing therapies can result in relatively high rate pacing episodes. A high-rate pacing episode could induce or exacerbate myocardial ischemia, putting the patient at risk for myocardial injury or serious arrhythmias.